A march to protest against Enrique Peña Nieto, of the Institutional Revolutionary Party, or PRI, who was declared the winner of the July 1 presidential election, drew thousands of people into the streets of Mexico City.
Some 5,000 people chanted slogans against Peña Nieto as they marched through the capital on Saturday, the Federal District Public Safety Secretariat said.
The protesters, a mix of students, adults and families, marched from the Angel of Independence monument to the Zocalo, Mexico City's largest plaza.
The march was organized by grassroots organizations and users of social-networking sites who contend that the general elections were plagued by a host of irrregularities.
Peña Nieto, according to the final tally released by the Federal Electoral Institute, or IFE, won the presidential election with 38.21 percent of the vote, while leftist candidate Andres Manuel Lopez Obrador ended up in second place, garnering 31.59 percent of the vote.
The results, however, have been challenged amid allegations of massive vote-buying by the PRI.
The protesters also vented against the IFE on Saturday, saying that the elections agency failed the people and calling on the TEPJF electoral court to "restore hope" to the country.
The electoral court has until Sept. 6 to issue a ruling on the challenge filed by Lopez Obrador's Progressive Movement coalition, either certifying Peña Nieto the winner or calling for a new vote.
Lopez Obrador also refused to accept the results of the 2006 presidential election, which he lost by a razor-thin margin to Felipe Calderon of the National Action Party, or PAN.
If its victory is ratified by the TEPJF, the PRI, which governed Mexico uninterruptedly from 1929 to 2000, will return to the presidency in December after 12 years of PAN rule.
During its 71 years of largely unchallenged hegemony, the PRI relied mainly on patronage and control of organized labor and the mass media, though it was not above resorting to outright vote-rigging and even violence.
Although many Mexicans remain suspicious of the party due to its corrupt past, the PRI was able to regain power in large part due to spiraling drug-related violence that has left more than 50,000 dead during the presidency of Calderon, who took office in late 2006.
The protest, however, was not organized by the "Yo Soy 132" student movement, which is holding a national convention this weekend in Atenco, a city in Mexico state that is the PRI candidate's hometown.
A group of Mexicans living in France, meanwhile, announced plans Sunday to ask the European Court of Human Rights in Strasbourg to investigate the alleged irregularities in Mexico's presidential election.
About 20 Mexican citizens plan to present a letter on Monday to the court. EFE